Driveline Vibrations

TrailHunter said:
What do you define as Thrust angle? I thought that was the rear axle being perpendicular to the centerline of the vehicle.
Click to expand...
You are right, my misuse of the term. What I'm actually referring to is the angle from the diff (pinion) to the driveline which is pinion angle. I'll go back and correct my posts. Thanks for pointing that out.
 
Last edited:
I believe my pinion angle is .5 degrees higher than my driveshaft. I've been told it should be at zero and I've also been told it should be 1-2 degrees lower 🙃
 
jrod1290 said:
I believe my pinion angle is .5 degrees higher than my driveshaft. I've been told it should be at zero and I've also been told it should be 1-2 degrees lower 🙃
Click to expand...
1-3 degrees seems to be the norm for most vehicles, but i'm pretty sure that doesn't account for lifted vehicles with large amounts of travel. My particular lift manufacturer actually recommended -1 degree to compensate for added flex and additional weight in the vehicle. When I called them to verify this they said anything between -2 and +2 is a good range. I think you are pretty good where you are at, every time you get in your vehicle or throw anything in the back that angle is going to change a bit. Pinion angle isn't static under use, It's all about not hitting an angle where binding or excess wear and tear happening when the axle is moving up and down.
 
Last edited:
So I'm guessing my last options here are to look into the T-case and pinion flanges? Bad gear setup? It didn't vibrate when I ran it with just the front shaft, but then again the rear diff was not under load.
 
jrod1290 said:
So I'm guessing my last options here are to look into the T-case and pinion flanges? Bad gear setup? It didn't vibrate when I ran it with just the front shaft, but then again the rear diff was not under load.
Click to expand...
You're best option is to verify the yokes are running true. Even a slight out of roundness as the drive shaft spins on either end will cause a bad vibration.
 
Thanks guys. Going to spend this weekend trying to get to the bottom of this. The one thing i have not been able to do is adjust the pinion angle. My upper control arms are as short as they go. My pinion is about 1 degree higher than the driveshaft. I keep seeing from multiple sources that it should be zero or even 1-2 degree lower than the driveshaft. I know the upper CAs are for pinion adjustment, but since they’re as short as they go - can lengthening of the lower CAs help lower the pinion angle? I know it’s supposed to just push the axle back, but I feel like it may also bring the pinion down?
 
jrod1290 said:
can lengthening of the lower CAs help lower the pinion angle? I know it’s supposed to just push the axle back, but I feel like it may also bring the pinion down?
Click to expand...
Yes, the statement that the uppers are for angle and the lowers are for wheel base only goes so far. It can always end up being a balance between the two.

lengthen the lowers just enough to get your pinion angle where it needs to be while still having a little adjustment left in the uppers.

It would be a good idea to flex it out after stretching the rear and check for rubbing issues.
 
UPDATE:
ITS FIXED!! I am so freaking happy! Okay so i adjusted the lower CAs to bring the pinion down a bit. My DS is at 9 degrees and my pinion is now at 7. I took it for a drive and the vibes were a lot better 55-60 but the vibes were still pretty annoying above 70. When i got back i disconnected the DS at the pinion flange and turned it 180 just for shits and giggles (I had tried this already before rebalancing/replacing u-joints and didn’t work). It was my last resort since i had already made an appointment for Monday to get the flanges checked out. i put the driveshaft back on and took it for a test drive - LO AND BEHOLD i had zero vibes! Smooth as glass, oh man i couldn’t believe it. Thank you all for the replies and great advice, couldn’t have done with out y’all.
 
You must log in or register to reply here.
Top Bottom